The experimental apparatus is built up based on the simulation results from Sections 5.1.2 and 5.1.3. Its entity, shown in Fig. 5.17, is set up at Ln. 756, Zhongzheng W. Rd., Zhubei City, Hsinchu County, Taiwan, and the system layout was shown in Fig. 4.1. It is an open-field experiment that exist lots of variables so we need many sensors to know the information of environment which is already demonstrated in Chapter 4. A series of experiments were conducted in two cases, the effect of curtain and effect of battery. According to those experiments, the quantity of generated electricity as function of time is exhibited to show its power generating condition.
5.2.1 Wind Speed and Wind Direction
The wind speed and direction in environment were measured during the experiments proceeding. As shown in Fig. 5.18, the wind velocity and wind direction change significantly in the open field. In this unstable situation, starting torque plays an important role in power generation; therefore, the Savonius wind rotors with great starting torque are used in this situation, as discussed in Section 2.2.2.1. Even though the significant variation, wind direction still has its own regulation, called monsoon, in which the south wind blows in summer and the north wind blows in winter. Because of the monsoon, the parallel matrix system is oriented in south-north direction agreed with the wind so that the wind rotors can always face it. Thus, the angle of wind direction will not vary too much.
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Nevertheless, the wind direction has about 30° deviation to the facade of the parallel matrix system, which is shown in Figure 5.18 (b).
5.2.2 Effect of Curtain
The same as the fore-mentioned, the flow in open field has significant variation. Among these variations, wind velocity and wind direction are variables that we cannot control. Besides, hysteresis happens in data recording, meaning that the information data not only depends on its current environment but also on its past one. When the wind speed goes up, the rotational speed of wind rotors are not kept the pace yet. On the other hand, inertia keeps the speed of wind rotors while wind speed descends. This phenomenon happens especially at TSR higher than 1.0. Therefore, we discuss the experimental results below TSR 1.0.
The results system with and without curtain are shown in Figs. 5.19 and 5.20. In figures each point is one measuring point and the red line inside is its trend line. For easy to analyze those data, round off the TSR of data points and calculate average value and standard deviation (see Fig. 5.21). The error bar in figure is one standard deviation. In Figure 5.21 shows that performance of system with curtain is apparently higher than system without curtain during TSR 0.7 to 1.0. The maximum difference is 58% which happened at TSR 1.0 and the average difference from TSR 0.7 to 1.0 is 34%. However, the simulation results (see Figure 5.12) shows that the difference mostly occurred in low TSR but no difference in these experiment. The main reason is that the battery connects at second side of circuit generates about 50 V energy gap. While the generated power is lower than 50 V, no current will be generated. Only when the generated power is higher than 50 V, we can get current. On the other word, the generated
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power was “eaten” by battery. Therefore, we withdraw the battery from second side of circuit to confirm this phenomenon. Figs. 5.22 and 5.23 show the results of system with and without curtain which withdraws battery. We arranged Figures 5.22 and 5.23 to receive Fig. 5.24. In figure, the effect of curtain appears in low TSR, and its average difference is 19% from TSR 0.2 to 0.9.
Consequently, curtain indeed enhances the performance of system but the effect of battery needs to be conquered.
5.2.3 Effect of battery
According to fore-mentioned that the battery connects at second side of circuit generates about 50 V energy gap which cause no current while generated power is lower, we consider that whether performance of system can be improved by withdraw the battery from second side of circuit. Fig. 5.25 and Fig.
5.26 show the comparison between system with and without battery. In Figure 5.25, system with curtain reveals that the variation of system without battery is bigger than system with battery. System without battery from TSR 0.9 to 1.0 almost no change but 80% difference from TSR 1.0 to 1.1. On the other hand, Figure 5.26, system without curtain, also shows that variation of system without battery is bigger than system with battery. The Cp of system without battery suddenly rises up at TSR 1.0. Even though the performance is so unstable in system without battery, we did not observe that system without battery has higher performance. Consequently, withdrawing battery from second side of circuit not only cause fluctuation of performance but also no use in improving performance. In these experiment results, we can realize that battery has a function to stable electric energy.
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5.2.4 Power Generating Efficiency
After series of experiment, we accumulate recording data for two hours in four kinds of cases to receive average power generating efficiency of system which is listed at Table 5.2.
Table 5.2 Power Generating Efficiency Electric Energy
These calculations are according to Eq. (5-1).
𝑃𝑜𝑤𝑒𝑟 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑛𝑔 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐 𝐸𝑛𝑒𝑟𝑔𝑦 generating record is illustrated in Fig. 5.27. In figure, generated power is not a
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fix value but rise and fall with time. The orange part is generated electric energy.
If wind velocity is unstable 7 m/s, system can generate 5.3 kw∙hr a day in power generating efficiency 10%. This electric energy can supply four refrigerators usage. Conversion of electric energy into money is 39 NT dollars for wind power capacity less than 10 kW is 7.3562 NT dollars per kw∙hr.
5.3 Comparison between Simulation and Experimental Results